The present invention relates to curtain wall and glass wall construction in general and glass panel joints and units in particular.
Curtain wall construction began to be widely employed by architects in the 1950s. Techniques and components of curtain wall construction have allowed architects to design and construct multi-story buildings having a building-supporting interior framework which obviates the necessity for massive exterior walls to support the building. Instead, in curtain wall construction, exterior walls need only support their own weight and serve chiefly to protect the building's interior from external environmental factors such as wind, rain, snow, etc. Curtain walls are non-bearing walls which are themselves supported by either direct or indirect attachment to a building's supporting framework. In a typical multi-storY curtain wall building, curtain walls are supported by attachment to floor structures which transmit loads to an interiorly disposed vertical framework. Advantages of curtain wall construction include faster enclosure of buildings during construction and the possibility of making extensive use of glass. A metal curtain wall may be defined as a non-load bearing wall supported by, or within, a metal framework. Many materials such as metal, glass, plastic, or masonry may be used for panels which are carried by, or within, the framework.
Curtain walls have been classified according to the method of installation employed. There are at least four generally recognized systems such as; (1) stick; (2) unit; (3) unit and mullion; and (4) panel.
In the stick method, construction proceeds piece by piece on site, generally beginning with attachment of vertical mullions to a building support such as a floor. Mullion attachment is followed by installation of horizontal rails and panels.
In the unit method, large factory assembled frame units (which may be preglazed) have frame edges adapted to interlock with adjoining units and the interlocked frames form mullions and rails.
In the unit and mullion method, mullions are initially installed and then factory assembled framed units are attached to the mullions.
In the panel method, formed sheet metal or cast panels interlock with adjoining Panels similar to the unit method. The main distinction between panel and unit is that each panel is generally formed as a whole single part e.g. by stamping.
Disadvantageously, none of the above systems provides an insulating glass unit curtain wall having a smooth outer surface which is mullion and/or rail free. An all glass outer curtain wall would provide a smooth outer surface without ridges or troughs thereby making maintenance, such as window washing, easier. A more esthetically pleasing exterior appearance would also be presented. By elimination of metal outer framework members, corresponding glazing would be eliminated. In addition, leakage due to thermal expansion cracks could be reduced by less need to employ materials of varying coefficients of thermal expansion. Also, leakage due to excessive wear of glazing compounds bY rain water funneled in troughs formed by raised outer framework members would be eliminated. A critical obstacle to creation of an outer framework-free, all insulating glass unit curtain wall has been the lack of a butt joint which has sufficient strength to provide a weather tight seal, allows for thermal expansion and contraction, and also securely holds the insulating glass panel units to an interior framework of the building. It would also be desirable that such joint allow for easY replacement of a broken or damaged insulating glass panel after completion of construction of the building and perhaps after years of use.
The aforementioned disadvantages have been reduced or overcome and beneficial aspects achieved by the present invention as described below.